Method and apparatus for manufacture of dual coated sheet with pressure rupturable materials

ABSTRACT

Tandem coating of paper web on one side with a clay coat and on the other side with a coating of pressure-rupturable encapsulated materials with the clay coat applied first and with a calender immediately before the coating with the encapsulated materials.

United States Patent Inventor Thomas W. Busch Appleton, Wis.

Appl. No. 795,663

Filed Jan. 31, 1969 Patented Jan. 4, 1972 Assignee Appleton Papers, Inc.

Appleton, Wis.

The portion of the term of the patent subsequent to Oct. 27, 1987, hasbeen disclaimed.

METHOD AND APPARATUS FOR MANUFACTURE OF DUAL COATED SHEET WITH PRESSURERUPTURABLE MATERIALS 2 Claims, 2 Drawing Figs.

US. Cl 117/36.2, 117/64,117/68,117/119.8,117/156 Int. Cl 841m 5/22 FieldofSearch 117/36.2,

Primary Examiner-Murray Katz AttorneyMeDougall, Hersh, Scott & LaddABSTRACT: Tandem coating of paper web on one side with a clay coat andon the other side with a coating of pressure-rupturable encapsulatedmaterials with the clay coat applied first and with a calenderimmediately before the coating with the encapsulated materials.

METHOD AND APPARATUS FOR MANUFACTURE OF DUAL COATED SHEET WITH PRESSURERUPTURABLE MATERIALS This invention relates to the art of coated papers,and it relates more particularly to the method and apparatus for thefabrication of a two side coated manifold sheet in which at least one ofthe coatings is formulated with a pressure-sensitive material of thetype described in the patents hereinafter set forth.

This invention has application to the manufacture of a manifold sheetadapted for use as an intermediate sheet in a manifold assembly and inwhich the manifold sheet is sometimes referred to as a colorless carbon.It will be understood that the concepts of this invention will haveapplication also to the manufacture of other two side coated paperproducts in which one or both of the coatings contain materials whichare pressure-sensitive such as a coating containing pressure rupturablecapsules.

in the U.S. Pat. Nos. 2,299,693; 2,374,862; 2,548,366; 2,712,507;2,730,456; 2,730,457; 2,800,457; 2,929,736; 2,293,582; 3,020,171;3,104,980; and 3,129,103, description is made of a copy process andmaterials for use in the practice of same in which separate coatings areprovided on suitable carrier sheets in which one of the coatings isformulated to contain a liquid reactant such as a colorless dyecomponent dissolved in a liquid solvent and which is encapsulated inmicroscopic capsules uniformly distributed throughout the coating(hereinafter referred to as the emulsion coat), while the other coatingis formulated of clay or other particulate substance which is adapted toreact with the liquid in response to release from the capsules to form acolored image (hereinafter referred to as the clay coat). When thecoating containing the encapsulated liquid is positioned in surfacecontact with the clay coating, no color develops until pressure isapplied by pen, pencil, stylus, typewriter key, die impression or thelike, or by heat to rupture the capsules in the imaged areas whereby theliquid released from the ruptured capsule wets out the adjacentreceptive material in the clay coating to develop the image.

In a manifold assembly, the top sheet in the assembly will be fabricatedwith only its underside coated with the emulsion coat, while the bottomsheet in the assembly will be coated on its top side with only the claycoating. All of the sheets in between will be coated on the undersidewith the emulsion coat and on the top side with the clay coat in a twoside coated sheet.

Since the emulsion coat comprises the more expensive materials andtherefore represents the more expensive coating, it is desirable tofabricate the clay coat with a high degree of surface smoothness so asto be able to make more effective contact with the emulsion coat andmaximize the utilization of the encapsulated liquid released from thecoating. in the light of the fact that the emulsion coat is sensitive topressure which might rupture the capsules, it has been the practice tocoat the paper first with the clay coat whereby the latter can becalendered to smooth the coating before application of the emulsioncoat.

It is an object of this invention to produce and to provide a method andmeans for producing a two side coated paper of the type described inwhich the coatings are sufficiently smooth and uniform throughout thesurface of the sheet and wherein the coated sheet is relatively free ofcurl or roll so as to lie flat while processing and in the manifoldassembly.

More specifically, it is an object of this invention to provide a methodand means for the manufacture of two side coated paper in which at leastone side is coated with a composition containing pressure-sensitivecapsules; in which the dual coating can be carried out in a singlecontinuous multiple coating process; in which the dual coated paper isrelatively free of roll or curl, and in which the process can be carriedout in a simple and efficient manner, with a minimum amount of time,labor, and equipment.

LII

These and other objects and advantages of this invention willhereinafter appear, and for purposes of illustration, but not oflimitation, an embodiment of the invention is shown in the accompanyingdrawing, in which FIG. 1 is a schematic elevational view of a coatingmachine embodying the features of this invention, and

FIG. 2 is an enlarged perspective view, partially in section, of a dualcoated manifold sheet produced in accordance with the practice of thisinvention.

Although the invention is addressed to the method and apparatus for thedual coating of paper base stock, the problem sought to be overcome bythis invention arises primarily by reason of the unique characteristicsof the compositions with which the base paper is coated and to combinein a single low cost process what has previously been a two or threestep highcost process Briefly described, the emulsion coating isformulated of an aqueous composition containing rupturable microscopiccapsules of tanned gelatin containing a liquid color-forming ingredient,such as a colorless dyestuff dissolved in an organic solvent. There maybe included within the emulsion coating composition, a substantialamount (up to 50 percent by weight of the capsules) of a coarse, solidparticulate material, such as cellulose fibers suspended with therupturable capsules and in which a small amount of water-soluble bindermay be dissolved in the aqueous medium. For a more detailed descriptionof the emulsion coating, reference may be made to the examples in U.S.Pat. No. 2,71 1,375, and others of the patents heretofore set forth.

The clay coating comprises an aqueous system having clay, such asattapulgite clay or special kaolin clays, in finely divided form,suspended therein, with or without other fillers such as calciumcarbonate, silica gel, satin white and the like, and a small amount ofresinous binder. For a more detailed description and formulation of theclay coating composition, reference may be made to the examples in theaforementioned patents.

Referring now to the concepts of the invention in a method and apparatusfor the manufacture of intermediate sheets having dual coatings of thetype described on opposite sides of the paper base sheet, the paper rawstock, such as l3-pound manifolding bond, is supplied in the form ofrolls 10 mounted for free rotational movement on a spindle 12 supportedon the unwind stand 14. The web 16 of raw stock paper is passed from theroll 10 over a series of idler rollers and guide rollers 18 to a firstcoating station 20.

The first coating station comprises an applicator roll 22 in contactperipherally first with a pickup roll 24 and then with a metering roll26. The lower portion of the pickup roll 24 dips into the bath of theclay coating composition to pickup a layer of clay coating, a portion ofwhich transfers to form a layer on the peripheral surface of theapplicator roll 22. Before the applicator roll 22 engages the undersideof the paper web 16, it is engaged peripherally by the metering roll 26which is effective to smooth the layer of clay coating and to meter thelayer before contact for transfer to the paper. The described means fortransfer of a smoothly metered coating to the one side of the paper webis referred to as the three roll transfer" and is more fully describedin my copending application Ser. No. 555,154, filed June 3, l966, andentitled Web Coating System and Method." The applicator roll 22 engagesthe bottom side of the paper web 16 as it passes between guide rolls 30and 32 and a metered quantity of aqueous clay coating composition isapplied to the bottom side of the paper web. An amount corresponding toabout 3-6 pounds per 3,000 square feet of surface area is applied.

From the first coating station 20, the one side coated web is advanceddirectly to an air knife 34 which cooperates with the turning roll 36 tometer the coating on the surface of the paper and uniformly todistribute the coating composition over the surface thereof. The coatedweb is advanced, while wet with the clay coating composition, from theair knife through one section 42 of a drying oven maintained at atemperature of about 220 to 300 F. while supported on an endless belt44. The upper run of the belt is supported on rollers 46 arranged in asubstantially arcuate path through the dryer and, for this purpose, itis preferred to make use of a foraminous belt or a belt formed of avapor permeable material to enable the escape of water vaportherethrough when released from the coating. The endless belt 44 turnsabout rollers 48 and 50 outside the dryer and the return run passesthrough the dryer section to maintain temperature while being supportedon a bottom run of rollers 52 provided with a takeup roller 54 formaintaining the proper tension in the supporting belt. For a moredetailed description of the drying system, reference can be made to myUS. Pat. No. 3,311,499

Before application of the emulsion coating of encapsulated materials,the one side clay coated paper web is advanced in rapid sequence throughan in-line calendar, illustrated in the drawing as a five-roll calender61 with hard steel rolls. The calender step is effective to improvesmoothness, improve resistance to distortion on wetting, and reduceporosity of the paper whereby a desirable capsule coating can be formedwith the application of less of the more expensive capsule coatingcomposition. This not only gives a considerable savings in cost, butwet-out occurs more as a surface phenomenon instead of penetration, withthe result that higher speeds can be obtained with less curl or cocklein the dual coated manifold sheet.

Returning now to the drawing, the clay coated paper l6, with the driedclay coating 60 on the top side thereof, is passed through the calender61 and then over a series of guide rolls and tensioning rolls 62 to asecond coating station 64 where application is made of the aqueouscoating composition of the encapsulated materials, hereinafter referredto as the emulsion coating. This second coating station is of the sameconstruction as the first in that it comprises an applicator roll 66 incontact with the uncoated side of the paper web 16, a metering roll 72and a pickup roll 74, having its lower portion inserted in a bath of theemulsion coating composition in pan 76. The coating compositiontransfers from the periphery of the pickup roll to the periphery of theapplicator roll, and the amount applied by the applicator roll ismetered by the metering roll of the described three-roll transfer.Application is made while the web is supported between the guide rollers68 and 70. The composition is applied in coating weights of about 3-4pounds per 3,000 square feet of surface area.

From the coating station 64, the coated web is advanced to a second airknife 78 and over roller 80 which again operates to meter the amount ofcoating composition allowed to remain on the web and to distribute thecoating uniformly across the web. Following the air knife, the claycoated surface is engaged by one or more reversing smoothing rolls 82 tosmooth the coating by the reverse rolling technique. While suchreversing rolls are preferred for improving the smoothness of thecoating, they are not essential for the emulsion coat.

From the smoothing rolls 82, the web coated on both sides and turnedabout the roller 80 to position the dried clay coat lowermost with thewet emulsion coat uppermost, is advanced over a suction apron 84 andthen to an upper section 86 of the drying oven through which it iscarried on the surface of a supporting endless belt 88. The upper run ofthe belt is supported on longitudinally spaced-apart crosswise extendingrollers 90 arranged in an arcuate path through the dryer and the beltcontinues to support the web for a short distance beyond the exit of thedryer whereafter the belt turns downwardly and back about rollers forreturn through the oven. A takeup roller 92 is provided outside of thedryer for adjusting the tension of the belt. As with the belt 44, it ispreferred to make use of a vapor-permeable belt to enable the escape ofvapors therethrough during passage through the dryer.

The web 16 coated on one side with a dried emulsion coat 6|) and on theopposite side with a dried clay coat 94 is passed over a series of guiderollers and tensioning rollers 96 to a windup roll 98 mounted on awinder stand 100 and powered to wind the coated web onto the roll. Thusthe web is drawn through the coating apparatus and dryer under tensionsupplied by the windup roll.

While in prior processes, the coatings have been applied in the sameorder by first applying the clay coat and then the emulsion coat, suchcoatings have been applied in separate operations on separate machineswith a separate calender on a still other machine in between. Suchthree-unit process requires considerably more capital investment, space,and manpower, and the nonintegrated arrangement leads to problems oftransportation and scheduling which interfere with the fast economicalproduction of the manifold sheet.

Efforts have been made to combine the operation into a single one on themachine coating operations by first applying the emulsion coat and thenthe clay coat with the possible eiimination of the calender, but certainadvantages from the standpoint of quality and performance are achievedwhen the order is reversed and in-line calendering is employed immediately in advance of emulsion coating.

From the standpoint of economy, the capsule emulsion coating representsthe more expensive coating. Thus, in use, it is desirable to haveoptimum surface smoothness in the clay coat for optimum contact betweenthe emulsion coat and clay coat in the copy system, thereby to optimizethe utilization of the encapsulated liquid upon release from thecapsules.

Further, from the standpoint of economy, it has been found that when theclay coated paper web is calendered in the manner described immediatelyprior to wetting the paper with the aqueous emulsion coating, the amountof emulsion coating applied to the paper can be reduced and therebyfurther to reduce cost and weight without loss of performance.

From the standpoint of performance, it has been found that the improvedsmoothness and reduced porosity is retained even when the coated sheetis rewet with the aqueous emulsion coating in that less penetration ofthe aqueous emulsion coating occurs into the base paper. As a result,less moisture is required to be driven out of the paper whereby higherspeeds can be achieved in manufacture with less wrinkle or cockle in thedried sheet.

lt will be apparent that the invention which combines the tandemcoating, three-roll metering and high-speed drying in a continuousoperation on a single machine places less demand on previous orsubsequent processing equipment, improves quality, markedly reduces costof operation, greatly improves raw material utilization, as well as toproduce a better and more uniform product.

The tandem process described produces the described dual coated paper ofbetter quality, better copy quality, improved resistance to smudge dueto smoothness of the clay coating, improved character definition becauseof the elimination of coating pattern, minimum to no curl or cockle,less paper distortion-all at a lower material cost with less waste.

It will be further understood that numerous changes may be made in thedetails of formulation and operation, without departing from the spiritof the invention, especially as defined in the following claims.

l claim:

1. In the method for high speed production of a capsule coatedcarbonless paper having a uniform pressure-sensitive capsular coating onone side and an image receiving clay coating on the opposite side, thesteps, in the sequence set forth, of metering an aqueous clay coatingcomposition onto one side of an endless sheet of relatively nonabsorbentbond paper, advancing the clay coated sheet continuously through adrying zone for removal of moisture from the clay coating composition,calendering the clay coated sheet to smooth the coating and densify thepaper, metering an aqueous emulsion coating of pressure rupturablecapsules onto one side of the sheet opposite the clay coating as acontinuous operation immediately following the calendering step, andadvancing the dual coated sheet continuously through a drying sectionwhile the sheet is supported, with the emulsion coated side uppermost,on a supporting surface traveling at about the same linear speed as thepaper for removal of moisture by directing hot air jets onto the coatedside of the sheet while the sheet is supported in a relaxed state.

2. The method as claimed in claim 1 in which, while the clay coatedsheet is continuously advanced through the drying zone, the sheet issupported with the clay coated side upper-

2. The method as claimed in claim 1 in which, while the clay coatedsheet is continuously advanced through the drying zone, the sheet issupported with the clay coated side uppermost on a surface traveling atsubstantially the same linear speed as the paper for drying the coatingby directing hot air jets onto the coated side of the sheet while thesheet is in a relaxed state.